Dimethyl carbonate can be produced, for example, by method 1 and method 2 described below.
(Method 1)
FIG. 5 is a diagram for illustrating method 1 using a steam reformer system. The numerical value noted along each line etc. in FIG. 5 designates a carbon (C) number introduced into a plant or transferred from device to device.
First, natural gas containing steam etc. is steam reformed by an endothermic reaction in a steam reformer 1 to yield a synthesis gas comprising CO, CO2 and H2, and methanol (CH3OH) is synthesized by using this synthesis gas in a methanol synthesizing device 2. At this time, a large quantity of CO2 gas is discharged from combustion exhaust gas of the steam reformer 1 and a boiler, not shown. Next, the synthesized methanol is transported to a dimethyl carbonate (DMC) synthesizing place, where dimethyl carbonate is produced by adding carbon monoxide (CO) and oxygen (O2) to the DMC.
In the case of method 1, for example, if natural gas corresponding to carbon number 300 is used, a synthesis gas containing CO, CO2 and H2 corresponding to carbon number 200 is used to synthesize methanol, and CO2 corresponding to carbon number 100 is discharged as combustion exhaust gas of the steam reformer 1 and the boiler, so that CO2 of carbon number 110 is discharged by adding unreacted CO2 (carbon number 10) from the methanol synthesizing system. Also, in the separate DMC synthesizing place, methanol of carbon number 190 is used for DMC synthesis together with CO and O2, and finally DMC of carbon number 95×3 is produced. In method 1, DMC is produced from methanol by the following reaction:CO+(½)O2+2CH3OH→CH3OCOOCH3+H2O(Method 2)
FIG. 6 is a diagram for illustrating method 2 using a steam reformer plus a partial oxidation system. Compared with method 1, method 2 is characterized in that a partial oxidation furnace 3 is arranged on the upstream side of the methanol synthesizing device 2 and partial oxidation is performed by the oxidation furnace 3 to synthesize methanol.
Also, as a specific method for producing dimethyl carbonate, a technique has been known, for example, in which dimethyl ether and carbon dioxide are allowed to react with each other in the presence of alkali metallic salt and methyl iodide, by which dimethyl carbonate is produced without impairing the activity of catalyst (Japanese Patent Provisional Publication No. 11-80096 (No. 80096/1999)).